Our long term goal is to elucidate the etiology of essential or polygenic hypertension with a focus on the elucidation of genetic variants that underlie hypertension susceptibility and gene-environment interactions which exacerbate hypertension susceptibility and end-organ disease. The emerging importance of arterial stiffening measured as pulse wave velocity or PWV in clinical studies demonstrating the association of increased PWV and cardiovascular outcomes (stroke, coronary heart disease, and chronic kidney disease) has pinpointed a likely robust predictive parameter, but at the same time highlighted the need for animal model studies to address mechanisms. Accordingly, this research proposal focuses on RFA-stated goals: #1) to explore the temporal relationship between arterial stiffening and the development of hypertension in an animal model, and #2) to conduct cellular and molecular investigation of mechanisms that lead to conduit artery stiffening in the context of (essential/polygenic) hypertension. To accomplish this we have prioritized the following specific aims: Aim 1. Examine the temporal relation between large artery stiffening (measured as aortic PWV and strain, carotid PWV and strain via high-resolution ultrasonography), and the development of salt-sensitive hypertension (measured via non-stress 24/7 telemetric BP analysis of SBP, DBP, MAP and PP) and stroke in both male and female stroke-prone Dahl S rats. Aim 2. Define the temporal and spatial changes in aortic and carotid artery structure in all three vessel layers, along with putative gene expression changes that underlie Na-induced exacerbation and progression of arterial stiffness along the disease course of hypertension and its end-organ complications. Aim 3. Elucidate the role of genetic mechanisms in the causation of arterial stiffness in the context of polygenic salt-sensitive hypertension via genome-wide scan of F2[Dahl S x Dahl R]-intercross male and female rats identifying common and sex-specific quantitative trait loci (QTLs) that contribute to arterial stiffness individually or interactively. Altogether, these three aims will elucidate the relationship of aortic and carotid arterial stiffness to polygenic (essential) hypertension and stroke in a Na-induced stroke-prone hypertension rat model, as well as give insight into causal cellular, molecular, and genetic mechanisms.